1. Field of the Invention
The present invention relates to a side door collision detecting system for detecting collision to a side door of the vehicle and relates to an occupant protecting system, which protects an occupant of the vehicle when the collision occurs.
2. Description of Related Art
Japanese Unexamined Patent Publication H2-249740 discloses a system that inflates a side airbag when the system detects a collision of a subject to a side door of a vehicle by use of a pressure sensor installed in an interior enclosed space (air tank) of the side door of a vehicle. Hereinafter, the above-described system is named as a pressure based side door collision detecting system.
Also, a well-known method includes a safing sensor (impact sensor), which has a semiconductor acceleration sensor or a reed switch installed on a pillar of the vehicle or a floor of the vehicle. The safing sensor detects an impact of a side collision by use of the semiconductor acceleration sensor or the reed switch, which detects an impact force generated when the pillar or the floor is deformed, so as to inflate the side door airbag. Hereinafter the above-described method is named as an impact force based side collision detecting method.
The above pressure based side door collision detecting system advantageously detects any side collision, which takes place at any part of the side door, by use of the pressure sensor (door internal pressure sensor) installed in the enclosed space inside the side door. Also, the above impact force based side collision detecting method advantageously detects non-side collision, which does not take place on the side door, because the deformation of the pillar or the floor due to the non-side collision is detected in this method.
It is preferable to determine the side collision based on a logical conjunction of an output signal supplied by the door internal pressure sensor and an output signal supplied by the impact sensor, which detects the deformation of the pillar or the floor, in order to limit a faulty determination of the side door collision. Here, the faulty determination may be made due to an increased door internal pressure, which is not based on the side door collision, or due to the deformation of the pillar or the floor, which is not based on the side door collision. Thus, a degree of accuracy in detecting the side door collision is advantageously increased. For example, the collision may be detected based on the deformation of the pillar or the floor, and the collision location may be identified as the side door based on an increase of the door internal pressure. Also, even when the side door is strongly closed and the impact sensor outputs a large signal, the faulty determination of the side collision may be limited because the door internal pressure may not change very much at this time.
However, in the above combination system, the impact sensor installed on the pillar or the floor may disadvantageously output a small signal when a pole, which has a small collision area, such as a trolley pole or a stand, collides with an easily deformable side door. Also, the impact sensor installed on the pillar or the floor may be located away from the side door, which is the collision location. Thus, the deformation may take time to be transmitted to the impact sensor, and an attenuated signal due to the transmission may deteriorate a sensitivity of the impact detection.
The above conventional airbag inflating system for the side door collision and other airbag inflating systems have been desired to limit the faulty inflation of the airbag also to accurately detect the side collision to the side door without delay.